This invention relates to a lower limb prosthesis, and to an energy-storing shin component for the prosthesis.
An energy-storing lower limb prosthesis is known from U.S. Pat. No. 4,547,913 (Phillips). This device provides an integral shin member and forefoot in the form of a single blade of fibre-reinforced material, the shin member extending generally axially of the prosthesis with the forefoot cantilevered in the anterior direction and with a curved connection between shin member and forefoot in an ankle region of the prosthesis. The major surfaces of the blade forming the shin member extend in the medial-lateral direction. A second blade, also with its major surfaces extending in a medial-lateral direction, is rigidly connected to the shin member in the ankle region and extends in the posterior direction to form a resilient heel member. Since the shin member is substantially planar and extends substantially vertically with a cross-section having a high area moment of inertia about an axis generally aligned in the anterior-posterior direction and a relatively low area moment of inertia about a horizontal axis generally aligned in the medial-lateral direction, it acts as a leaf spring storing and releasing energy during the stance phase, by anterior-posterior bending whilst being comparatively rigid with respect to transverse bending moments. This prosthesis is particularly useful for active amputees, including those wishing to take part in sports activities.
A disadvantage of this known device is that the energy-storing capabilities are achieved at the expense of versatility, in the sense that a wide range of sizes and stiffnesses must be produced to suit different amputees, particularly with regard to foot size. Although in the case of below-knee lower limb prostheses, the device may be connected to a stump socket by means of a clamp or flange attached to the proximal end of the shin member, in some situation the length of the shin member becomes comparatively short with consequent loss of energy-storing capacity. This is particularly the case with prostheses for amputees having long below-knee stumps.
It is an object of this invention to provide a versatile shin component for a below-knee prosthesis.